Xanthophyll is a kind of carotenoid, which generally exists in flowers, leaves and fruits of plants as well as certain kinds of algae, especially exists in great quantity in marigold petals. Xanthophyll exists in plants in the form of a xanthophyll ester. Xanthophyll is generally obtained by saponifying an extract of plants in this industry. Recently, the biological functions of xanthophyll are drawn more attention. Xanthophyll has a strong effect of antioxidation and removes the harmful “free radicals” produced during the physiological metabolism process in human body. The “free radicals” are found to lead to lesions such as tissue damage, cell aging and the like. Early in 1995, xanthophyll is approved by FDA to be a supplement in food and drink. In the “list of new food additives and food flavorants (No.8 public announcement of the Ministry of Health of China in 2007)” announcement recently published in China, xanthophyll can be used in food as a colorant and nutrient supplement.
Since xanthophyll has a complex molecular structure, the industrial synthesis thereof is very difficult. However, natural xanthophyll in plants has a lot of advantages such as natural, nonhazardous, relatively low cost for extracting and purifying and being suitable for production in large scale. Although currently the production of xanthophyll resin achieves a large scale, most of the xanthophyll is produced in form of oleoresin with impurities. Therefore, they are suitable to be used only as animal food but lack safety for using in human food as colorants and nutrient supplements.
U.S. Pat. No. 5,648,564 discloses a process for extracting a xanthophyll crystal from plants, wherein xanthophyll oleoresin is dissolved with propylene glycol, alkali solution is added thereto for saponification at a higher temperature, water is added thereto and the crystals formed are filtered, and then the crystals are washed and dried to obtain a xanthophyll crystal. Since the propylene glycol used in the process has a higher boiling point, it is difficult to recover the solvent; and the final product has a purity of about 70% only and yield of about 60% only, which are relatively lower.
U.S. Pat. No. 6,743,953 discloses a process for separating and purifying xanthophyll from marigold oleoresin, wherein the oleoresin or xanthophyll ester is firstly saponified and then concentrated to obtain a concentrated solution, water is added thereto to dilute the concentrated solution, the resulting solution is extracted with ethyl acetate, and then concentrated to obtain a xanthophyll crystal. The xanthophyll obtained in this process has low purity, and large amount water used in the process is apt to cause environment pollution, and the yield of xanthophyll is relatively low.
U.S. Pat. No. 7,150,890 discloses a process for extracting xanthophyll from marigold petals, comprising the following steps: saponifying the dried petals; diluting the saponified liquid with water; adding metallic halide to the mixture in order to adjust the pH value of the mixture; filtering the pH-adjusted mixture to get a resultant solid; and then washing the resultant solid with a polar solvent to provide xanthophyll. Since the dried marigold petals are saponified directly in the process, the efficiency and yield of saponification is relatively low; the marigold flowers needs to be dried before extraction, and the time period for drying is too long and thus affects the production scale; using metallic halide to adjust the pH value leads to a extracting solution containing a large amount of metallic ions, which is apt to an environment pollution.
Process for preparing a xanthophyll crystal disclosed in China comprise: adding water or alcohol for crystallization after saponification, filtering the mixture to obtain coarse xanthophyll, and then recrystallizing the xanthophyll. A large amount of waste water is produced in the process, and the time period of the preparing process is prolonged, which is unfavorable for the stability of xanthophyll.